Safety device for quick-fit attachments used for fitting a tool to the end of the arm of a hydraulic excavator

ABSTRACT

Safety device for quick-fit attachments comprising two parts ( 1 ) and ( 2 ), of which one ( 1 ) is borne by the arm of the digger while the other ( 2 ) is secured to the tool (for example a dipper), said first part having a cradle ( 3 ) formed by a pair of hooks, able to grasp hold of a shaft ( 4 ) belonging to the second part in order to raise the tool and allow the first part to pivot so that the two parts can be pressed against one another to allow for locking, characterized in that each part of the attachment has a member ( 7 ) able to collaborate with a member ( 8 ) of the other part if the weight of the tool being picked up does not exceed the capacity of the digger, collaboration being impossible when such is not the case, so that the first part is unable to be pressed against the second and locking is prevented.

The present invention relates to a safety device for quick-fit attachments. A “quick-fit attachment” is a device which makes it possible to fix a tool to the end of the arm of a hydraulic excavator or the like, which is referred to below as “the machine”.

A “quick-fit attachment” is a mechanical device comprising two parts, of which one is fixed to the tool, for example a dipper, while the other is borne by the arm of the machine.

The prior art on the subject is constituted, in particular, by document FR 2946061.

This document describes an attachment, of which the first part, which is substantially stirrup-shaped and integral with the arm of the machine, comprises a cradle formed by a pair of hooks which is capable of being inserted under a shaft belonging to the second part borne by the tool.

Said second part has a hook-shaped extension which is capable of passing through an opening in the first part and an opening in a sliding locking plate which is capable of being inserted under the said extension when the two parts are pressed against one another.

Means are provided for keeping the locking plate in the “armed position”, that is to say in a position in which the hook-shaped extension is capable of passing freely through the median portion of the first part and the locking plate.

When passing through the two openings, the hook-shaped extension frees the locking plate which, under the action of springs, is inserted under the said extension.

Generally speaking, a quick-fit attachment is designed to be capable of being used with a range of machines having different sizes (and therefore different weights).

Furthermore, it is known that a machine must not shift a load, including the tool, the weight of which exceeds about 15% of its weight. If so, since the load is excessive, the machine may topple over and cause an accident.

In the current state of the art, it has to be recognised that a “small machine” may catch hold of, and handle, a dipper whose weight exceeds the machine's capacity.

The present invention, which has the object of remedying this drawback, relates to a safety device which positively prevents the locking of a dipper whose weight, when loaded, exceeds that of the machine.

Since it is known that the locking of a dipper can only take place on condition that the two parts of the attachment are pressed against one another, the safety device belonging to the invention utilises means, the effect of which is to resist this pressing action if the dipper to be caught hold of exceeds the machine's capabilities.

According to the invention, each part of the attachment has a member which is capable of cooperating with a member belonging to the other part if the weight of the tool, when loaded, does not exceed the capacity of the machine, said cooperation being impossible if this is not the case, so as to resist the pressing of the first part onto the second and to prevent locking.

The present invention will be better understood by means of the description that will follow, by referring to the drawings which are appended solely by way of an indicative example and in which:

FIG. 1 shows, in a vertical section and in perspective, the two parts of the attachment prior to the start of the hitching operation;

FIG. 2 is a view similar to FIG. 1, showing the two parts of the attachment at the start of the hitching operation;

FIG. 3 is a view in perspective showing the dipper locked onto the machine, the locking plate not being represented;

FIGS. 4 to 7 are diagrammatic views which explain the functioning of the safety device belonging to the invention; and

FIGS. 8 and 9 are diagrammatic views similar to FIGS. 4 and 7, showing a variant of embodiment.

According to the known art, the attachment comprises two parts 1 and 2, the part 1 being fixed to the arm of the machine (not shown) while the part 2 is fixed to the upper part of the dipper G.

The part 1 has a pair of hooks 3 which are capable of catching hold, as a result of judicious manoeuvring of the arm of the machine, of a shaft 4 which is borne by the part 2, and of lifting the dipper.

By causing the part 1 to pivot in the direction of the arrow F₁, the usual extension 5 passes through the opening in the median part of the part 1 and also through the opening in the locking plate 6, freeing the latter which, when the two parts are pressed against one another, slides in the direction of the arrow F₂ so as to be inserted under the said extension 5.

According to the invention, the part 1 has a member which is constituted by a finger 7 which is capable of being inserted freely in a member constituted by a slot 8 in the part 2, the dimensions of the said two members depending upon the size of the machine and of the dipper in such a way that the finger borne by a “small machine” cannot penetrate into the slot in a “large dipper”, although the reverse is naturally possible.

According to one mode of embodiment, FIG. 4 shows a finger 7, the width of which is substantially equal to the width of the slot 8; the said finger is capable of penetrating freely into the said slot and locking is possible. The finger 7 is borne by a small machine and the slot 8 is borne by a small dipper.

FIG. 5 shows a finger 7 a which is narrower than the finger 7 and is borne by a large machine. Since the finger 7 a easily penetrates into the slot 8, the locking of a small dipper onto a large machine is therefore possible.

As is apparent from FIG. 6, a large dipper is associated with a slot 8 a which is narrower than the slot 8 and is capable of cooperating with a finger 7 a.

On the other hand, as is apparent from FIG. 7, a large dipper with which a narrow slot 8 a is associated cannot be locked onto a small machine with which a finger 7 which is wider than the said slot 8 a is associated.

According to one variant of embodiment (FIG. 8), the part 1 is cut out in such a way as to have a projection 9 which is capable of penetrating into a recess 10 in the part 2 if the dipper to be caught hold of does not exceed the capabilities of the machine.

FIG. 9 shows a dipper G whose weight, when loaded, exceeds the capabilities of the machine and the edge 10 a of which is offset in relation to the edge 9 a of the part 1, so that the projection 9 on the “small machine” cannot penetrate into the recess 10 on a “large dipper”.

It is apparent from the explanations given above that the safety device is disposed on the sides of the parts 1 and 2 which extend parallel to the shaft 4, but a similar result could be obtained if the said device were situated on at least one of the sides which extends substantially at right angles to the said shaft. 

1. Safety device for quick-fit attachments, comprising two parts (1) and (2), of which one (1) is borne by the arm of the machine while the other (2) is secured to the tool (for example a dipper), the said first part having a cradle (3) formed by a pair of hooks which is capable of catching hold of a shaft (4) belonging to the second part in order to raise the tool and allow the first part to pivot in order to press the two parts against one another to allow locking, characterised in that each part of the attachment has a member (7 or 9) which is capable of cooperating with a member (8 or 10) belonging to the other part if the weight of the tool, when loaded, does not exceed the capacity of the machine, said cooperation being impossible if this is not the case, so as to resist the pressing of the first part onto the second and to prevent locking.
 2. Device according to claim 1, characterised in that, according to one mode of embodiment, one of the members is constituted by a finger (7) which is capable of penetrating into a slot (8) in the other part, safety being ensured by judiciously dimensioning the slot and finger according to the size of the machine and of the tool in such a way that the finger belonging to a small machine cannot penetrate into the slot belonging to a tool whose weight, when loaded, exceeds the capabilities of the said machine.
 3. Device according to claim 1, characterised in that one of the members is constituted by a projecting part (9) which is capable of penetrating into a recess (10) in the other part, safety being ensured by judiciously positioning the edge (9 a) of the said projection in relation to the edge (10 a) of the said recess in such a way that the projection belonging to a small machine cannot penetrate into the recess belonging to a tool whose weight, when loaded, exceeds the capabilities of the said machine. 